So part of the theory is that Kirby is a victim of interdimensional travel (again) and winds up in a place that doesn’t look quite like earth, the main difference being the language. It looks very similar to the Koppai language though I believe it could also be a more advanced form of the Hocatate language but there isn’t much to support that to my knowledge.

Assuming it is Koppai, we learn in Pikmin 3 the planet is on the brink of extinction but is saved after enough food is brought back. We also know they’re pretty advanced as far as tech goes which would explain the lab we go into towards the end of the game. It’s possible they decided to prepare for the next threat and performed an experiment or two which would give them enhanced abilities, like Leongar or the experiment behind him to outlive any event that may happen.

The only issue arguably is size but in Kirby forgotten land we do see Kirby being stretched and twisting into various shapes, but despite the pikmin series taking place on earth making Olimar the size of a coin roughly.

I also want to point out a small easter egg in galaxy, where we see a ship from the pikmin series in junkyard galaxy. Mario is small enough there to stand in one of the cockpits where a crystal sits, making olimar a similar size to him, and the same for Kirby based on the height chart in smash.

The only thing that makes me believe it’s on Hocatate is that we do see Louie and Olimar essentially selling stuff to Hocatate from Earth to pay off the debt. Though it’s possible the company that was getting this data was selling it for that money, meaning the koppai could’ve gotten some of it.

We also know in the Kirby series that there are characters and beings well capable of interdimensional travel, and Leongar points out that the beast pack was left behind in that dimension, and there were two groups in Kirby, one dealing in tech, like what we see Magalor using with the Lor starcutter, or ones that deal with more powerful beings and magic, like hyness. It’s possible the koppai could’ve come in contact with one of the more magical ones if they were responsible for the beast pack, and went to another dimension, leaving them behind to try and salvage that world in a sort of Wall E way.

It’s a bit of a stretch but hey, that’s just a theory.